Safety of optical fiber networks in potentially explosive areas

Explosion protection is indispensable for many industry sectors. Facilities operating in potentially explosive areas have to demonstrate the necessary approvals. This not only applies for the system as a whole, but also for the individual components. There are relevant standards and directives in place to ensure this, such as ATEX, according to which, components for industrial Ethernet also have to be certified. Contrary to common assumption, fiber optic components also have to meet strict directives if they are to be deployed in explosion hazard areas, because even the luminous power emitted under certain circumstances represents a risk of explosion that should not be underestimated.

Explosion protection is important for far more industry sectors than one may perhaps presume. Anyone questioned on the matter thinks firstly of mining where gases ("mine gas") and dust represent major explosion hazards. But there is far more to it than that: Companies producing and processing mineral oil and natural gas, the chemical industry, the coating and paint industry, pharmaceutical companies, petrol stations, fuel depots, but also agriculture with biogas, livestock gases and dust, wood processing firms (wood dust), and even metal processing firms (metal dust, particularly light metals) and mills (flour dust). An elevated explosion risk prevails everywhere here.

Without a source of ignition, no explosion

Devices used in potentially explosive areas have to be designed and constructed in such a way that both in normal operation and also in the event of a fault they never produce an energy density that is sufficient to ignite ambient gases and dust. This also includes the situation in which the device is damaged or destroyed by extraneous influences.

This is easier said than done. Almost everything that has a high energy density can serve as a source of ignition, and this includes many more than you think: hot surfaces, flames, hot particles, sparks, radio waves, ultrasound, shock waves and even luminous power. All this has to be taken into consideration in the design and operation of facilities and devices.

Light is problematic too

Even light can have such high energy densities that ignition of explosive atmospheres may occur. What can be done?

A non-ATEX approved electronic device can generally be accommodated in a pressure-resistant enclosure, but this is less suitable for applications in data technology, as the device and its connections are then inaccessible for maintenance work or for connecting and disconnecting patch cables.

But even if the electronic device is in a pressure-resistant enclosure or is accommodated outside the zone, the data lines still pass through potentially explosive areas and therefore pose a risk that should not be underestimated. If the cable jacket of a fiber optic cable is damaged or a glass fiber breaks, light can escape and lead to ignition of explosive atmospheres. The same applies if a plug is pulled out in a potentially explosive environment - whether inadvertently or intentionally - or if it detaches in ongoing operation, due to vibration or tension on the cable, for example. The open end of a glass fiber cable also represents a safety risk, or also a connection in a patch panel, a junction box or the free end of a patch cable.

In all these cases encountered in practice, under certain circumstances luminous power can escape, which has such a high energy density that an explosion may occur. If you wish to effectively prevent these hazards, it is necessary to only use electronic devices and components whose luminous power is so reliably limited that they do not qualify as sources of ignition.

MICROSENS takes this approach with its ATEX SFP transceivers.

Practically viable 1.25 Gbps

As a pioneer in glass fiber technology, MICROSENS has developed an SFP transceiver that limits the energy density of the emitted light. It is so low that the light cannot serves as a source of ignition. Not even in the case of cable breakage.

The transceiver fulfils DIN EN 60079-28 for inherent optical radiation ("op is") and is certified in accordance with ATEX Directive 1999/92/EC; the full ATEX marking is EX II(1)G [Ex op is Ga T4] IIC. MICROSENS had its own production facilities certified to DIN EN ISO/IEC 80079-34 for the manufacture of the transceiver.

The transceiver works protocol transparent with data rates up to 1.25 Gbps and is therefore universally suitable for Fast Ethernet, Gigabit Ethernet, as well as Fibre Channel, ATM and Sonet applications. It offers diagnostics functions that are compatible with the SFF-8472 specification.

Thanks to its robust technology and the extended temperature range of -40°C to +85°C, it is suitable for industrial applications and outdoor use alike. Application areas include oil and gas production, shale gas drilling fields, pits and quarries above ground, conveyancing facilities or pipelines. Classical Ex areas can also profit from the advanced technology, such as refineries and petrochemical plants, installations of the chemical industry or also large livestock facilities.

Conclusion

With the ATEX-certified SFP transceiver from MICROSENS, the industrial user at last has a component at their disposal with which high data rates of up to 1.25 Gbps can be transmitted safely and reliably through Zone 0 potentially explosive areas. As a result of its robust technology and the temperature range of -40°C to +85°C, it is suitable for both indoor and outdoor applications.